Apparatus for testing ductility of sheets

ABSTRACT

This invention relates to apparatus for testing the ductility of sheet materials such as sheet metal.

Unlted States Patent 11 1 1111 3,736,794

Biondi 1 51 June 5, 1973 [54] APPARATUS FOR TESTING DUCTILITY OF SHEETS[56] References Cited [75] Inventor: Frank J. Biondi, Brooklyn, NY.UNITED STATES PATENTS Assigneel The United Slates of America 881,371,050 3/1921 Olsen 73/87 represented by the United States 1,395,24711/1921 Abrams ..73/38 Atomic Energy Commission Washington, DC.2,262,084 11 1941 Alexander ..73 87 Filed: P 2, 1946 PrimaryExaminerSamuel Feinberg [211 App No 265 894 Att0rneyRoland A. Anderson[57] ABSTRACT This invention relates to apparatus for testing the duc fht t h h t taL 58 Field of Search ..73/s7,94,102,37, S 66 m emssuc ass asme 73/38, 40, 46, 52 4 Claims, 3 Drawing Figures PATENTEUJUN 5 I975SHEET 1 UF 2 INVENTOR F. J. BIO/VD! ATTORNEY APPARATUS FOR TESTINGDUCTILITY OF SHEETS Essentially the apparatus in its preferred formcomprises two members adapted to clamp therebetween a sheet specimen ofthe material to be tested. One of the members is provided with means forurging a spherical element against the specimen to be testedsufficiently to crack or rupture the specimen. The other of the memberscontains a closed chamber, one wall of which is formed by the specimento be tested, and in which chamber is maintained an air pressuredifferent from that of the atmosphere, preferably a lower pressure.Means for detecting a change in the pressure in the chamber isassociated with the member containing the chamber. When the specimen iscracked or ruptured, the pressure in the chamber changes abruptly andthe change may be readily detected. Thus is provided a means for easilyand accurately detecting when the specimen is cracked or ruptured. Bycorrelating this indication with the amount that the spherical elementhas deformed the specimen before cracking or rupturing, a measure of theductility or similar characteristic of the specimen can be obtained.

The construction and operation of the apparatus will be more readilyunderstood from the following discussion in connection with theaccompanying drawings in which:

FIG. 1 is a side view of the apparatus, partly shown in section;

FIG. 2 is an enlarged view partly in section of the specimen rupturingmechanism of FIG. 1; and

FIG. 3 is similar to FIG. 2 except the view is taken from a differentangle.

Referring to the drawings, a metal vertical member is shown mounted on asuitable base 9. The vertical member 10 is provided with a horizontalslot 11 to receive a test specimen 12. Below the slot 1l is a verticalthreaded hole 13 in which is threaded a power-driven rotatable spindle14, the upper portion of said spindle being provided with a cylindricalelement 16. The upper portion 15 of this element 16 has the shape of ahalf sphere and is adapted to contact specimen 12. The spindle shaft 14may extend to below the sprocket wheel 28. The apparatus also comprisesan upper member 6 threaded in the portion 8 of the base member 10 abovethe slot 11 and adapted to clamp the specimen against the portion 7 ofthe base member 10 below slot 11 with an air-tight seal. The uppermember 6 is provided with a chamber 17, the upper end of which is closedwith some suitable material 18 which may be glass or a transparentplastic materia; the lower end of the chamber is closed by the specimen12 to be tested. The upper member 6 is screwed down and clamped tightlyagainst the specimen 12 by means of the handle At the lower end of thespindle shaft 14 is a dial 23 and a sprocket wheel 28. Said sprocketwheel is con- At the beginning of the operation before the specimen 12is placed in the device the element 15 is set so that its top level willbe just beneath the specimen 12 when the latter is inserted. This isdone by turning on the motor 26 and allowing the spindle 14 to rise inthe threaded hole 13 until the top of the element 15 has just reachedthe level of the slot 11, whereupon the motor is turned off. Theposition of the element 15 may be observed by looking through thetransparent disc 18. If desired, during the adjustment of the element15, a glass slide may be inserted in the slot 11 in place of thespecimen 12. If the element 15 is pushed beyond the level of the slot11, the glass slide will crack.

After setting the element 15 in position it is desirable to arrange thescale 25 and the dial 23 so that they read zero revolutions. This may bedone by loosening the screws 40 in the scale 25 and sliding the scalethrough the slot 39 until the dial 23 is just level with the zero markon the scale 25. The dial 23 may then be set at its zero point byloosening the nut 30 which disengages the dial from the spindle shaft 14so that the dial may be rotated around the shaft in any direction. Whenthe dial has been set so that its zero point corresponds with the zeropoint on the scale 25, the nut 30 is tightened again so that the dial isheld firmly against the spindle shaft 14 between the nut 30 and theblock 41, said block being a support for the dial.

The specimen '12 is now inserted into the slot 11 and is clamped inplace by turning the handle 19. The appearance of the specimen at thispoint is as shown in FIG. 2. The vacuum pump (not shown in the drawings)is then started after which the motor 26 is turned on, which causes thespindle shaft carrying the element 15 to move upward so that the element15 is pushed against the specimen 12. When the limit of the ductility ofthe specimen 12 is reached, the specimen ruptures and has the appearanceof the specimen shown in FIG. 1. At this point the motor 26 is turnedoff causing the spindle shaft 14 to stop moving.

While the spindle 14 is being pushed upwards, a negative pressure ismaintained in the chamber 17 by means of a vacuum pump;'if the specimenis porous as in the case when slightly porous materials are beingtested, air passes through the specimen at a constant rate while anegative pressure is maintained in the chamber. When the sphericalelement 15 carried by the spindle 14 cracks or ruptures the specimen 12,the rate of flow of air into and from the chamber 17 is changed, and thepressure therein is changed. The air rushing into the chamber 17,because of the rupture in the specimen 12, causes a sudden movement ofthe liquid in the manometer 21 which may be readily detected by the eye.This movement of the liquid in the manometer is the signal for the motorto be turned off. The rate of flow of the air into the chamber 17 may bedetermined by the rate of the movement of the liquid in the capillaryflow meter 22. Any suitable liquid such as mercury, oil, or water may beused in the manometerand the flow meter.

The tube 38 contains a capillary member 42 which allows the air passingthrough the system to enter the flow meter 22 slowly, so that the rateof flow of air into the system may be determined.

Since the spindle shaft 14 and the dial 23 are attached to one anotherso that they move as one unit, the dial 23 will make one revolution foreach revolution made by the spindle shaft. The number of completerevolutions made may be read from the scale 25 while the fractionalparts of revolutions may be read from the dial 23 which is marked toread to one hundredth of a revolution. The number of revolutions made isan indication of the force necessary to apply to the element 15 to causeit to rupture the specimen 12. Thus the number of revolutions made bydial 23 from the zero point to the point where the specimen rupturesgives an indication of the ductility of the specimen.

The element 15 is shown in the drawings as a sphere but it may be madein other shapes, such as a pyramid or an oval; the shape used depends onthe test to be made. If a sphere-shaped element is used, it may be ofany suitable size; a sphere with a fairly large diameter is preferredfor a brittle specimen, while a small sphere is preferred for moreductile specimens. In general it is preferable to relate the element 15to the spindle 14 in such a waythat the element will not rotate as thespindle 14 is moved upward.

If the element 15 is rotated with the spindle 14, the force exerted onthe specimen 12 would be partly a rotational force rather than a forcedue to the upward thrust of the element 15. One way to prevent theelement 15 from rotating is to form the element as an integral part of acylinder 16, with the cylinder 16 resting freely on the top of spindle14. To keep the cylinder 16 in place a pin 31 may be inserted into acavity of the cylinder. The pin 31 travels up and down in a verticalgroove 32 in the casing as the spindle moves up and down in the hole 13.

Materials of a wide range of ductility may be tested by this device,such as the most ductile materials or materials which are so brittle asto be difficult to handle. Since the clamping members 6 and 7 determinethe area tested no special preparation of the edges of a sample must bemade to avoid cracks or imperfections as is necessary in tensilestrength or elongation testing.

In the illustrated apparatus the dial 23 may consist of two discs oftransparent methylmethacrylate with ground beveled edges having a pieceof black paper sandwiched between them. The dial is edge lighted by lamp24 as it moves, and the light is transmitted by the synthetic resin togive a sharply contrasted, easily read black line at the periphery. Avertical scale 25 records the number of revolutions made by the dial 23.The dial itself may be marked to read to one-hundredth of a revolution.When the motor 26 is reversed to lower the spindle 14, at about the timethe dial 23 reaches the zero position, the sprocket wheel 28 is engagedby a plunger type switch 27 which disconnects the motor 26 from itssource of power. The switches 36 are used to control the motor 26 andthe lamp 24.

This invention is particularly adapted for testing the ductility ofporous metal sheets of such porosity that they are capable of use asbarriers for the separation by diffusion of gases from mixtures ofgases, where the gases in the mixture pass through the pores primarilyby molecular or diffusive flow as distinguished from plain or viscousflow.

Various modifications may be made in the illustrated apparatus, and theapparatus is susceptible of use for other purposes. Materials such aspaper or plastic sheets and films as well as materials may be tested bythis apparatus.

What is claimed is:

1. An apparatus for testing ductility comprising two members adapted toclamp a piece of material therebetween, one of said members having aclosed chamber therein one wall of which is formed by the specimen beingtested, an element associated with the other member for deforming thespecimen, means for measuring the movement of said element, means formaintaining in said chamber a pressure different from that of theatmosphere, and means for detecting a change in said pressure due tocracking of said specimen when it cracks because of deformation by saidelement.

2. An apparatus for detecting the ductility of material in sheet formcomprising two members adapted to clamp a sheet of materialtherebetween, one of said members having a closed chamber'therein onewall of which is formed by the specimen being tested, an elementassociated with the other member for deforming the specimen, means formeasuring the movement of said element, means for maintaining in saidchamber a pressure lower than that of the atmosphere, and means fordetecting a change in said pressure due to cracking of said specimenwhen it cracks because of deformation by said element.

3. An apparatus for detecting the ductility of material in sheet formcomprising two members adapted to clamp a sheet of materialtherebetween, one of said members having a closed chamber therein onewall of which is formed by the specimen being tested, an elementassociated with the other member for deforming the specimen, means formeasuring the movement of said element, means for maintaining in saidchamber a pressure different from that of the atmosphere, means fordetecting a change in said pressure due to cracking of said specimen,said means comprising a manometer, and means for detecting the rate offlow of gas through the deformed specimen, said means comprising a flowmeter.

4. An apparatus for detecting the ductility of material in sheet formcomprising two members adapted to clamp a sheet of materialtherebetween, one of said members having a closed chamber therein onewall of which is formed by the specimen being tested, the other of saidmembers comprising a spindle placed in an aperture, said spindle beingcapable of moving to and fro in said aperture, an element for deformingthe specimen associated with said spindle, said element adapted to bethrust against said specimen until said specimen ruptures, means formeasuring the movement of said element, means for maintaining in saidchamber a pressure different from that of the atmosphere, and means fordetecting a change in said pressure due to cracking of said specimen.

1. An apparatus for testing ductility comprising two members adapted toclamp a piece of material therebetween, one of said members having aclosed chamber therein one wall of which is formed by the specimen beingtested, an element associated with the other member for deforming thespecimen, means for measuring the movement of said element, means formaintaining in said chamber a pressure different from that of theatmosphere, and means for detecting a change in said pressure due tocracking of said specimen when it cracks because of deformation by saidelement.
 2. An apparatus for detecting the ductility of material insheet form comprising two members adapted to clamp a sheet of materialtherebetween, one of said members having a closed chamber therein onewall of which is formed by the specimen being tested, an elementassociated with the other member for deforming the specimen, means formeasuring the movement of said element, means for maintaining in saidchamber a pressure lower than that of the atmosphere, and means fordetecting a change in said pressure due to cracking of said specimenwhen it cracks because of deformation by said element.
 3. An appaRatusfor detecting the ductility of material in sheet form comprising twomembers adapted to clamp a sheet of material therebetween, one of saidmembers having a closed chamber therein one wall of which is formed bythe specimen being tested, an element associated with the other memberfor deforming the specimen, means for measuring the movement of saidelement, means for maintaining in said chamber a pressure different fromthat of the atmosphere, means for detecting a change in said pressuredue to cracking of said specimen, said means comprising a manometer, andmeans for detecting the rate of flow of gas through the deformedspecimen, said means comprising a flow meter.
 4. An apparatus fordetecting the ductility of material in sheet form comprising two membersadapted to clamp a sheet of material therebetween, one of said membershaving a closed chamber therein one wall of which is formed by thespecimen being tested, the other of said members comprising a spindleplaced in an aperture, said spindle being capable of moving to and froin said aperture, an element for deforming the specimen associated withsaid spindle, said element adapted to be thrust against said specimenuntil said specimen ruptures, means for measuring the movement of saidelement, means for maintaining in said chamber a pressure different fromthat of the atmosphere, and means for detecting a change in saidpressure due to cracking of said specimen.